Boba_Fret Posted October 6, 2004 Report Share Posted October 6, 2004 (edited) First of all I am new to electronics. I thought it would be a good little hobby to get into to help pass the time. It isn't working out that way. I have been trying to wrap my head around the designs for the "Little Gem", "Little Gem MKII", and "Ruby" LM386 guitar amps, but it's all going right over my head. What I want IS: to make a guitar amplifier into a cigarette box, that has guitar jack In & Out, a small speaker, and a headphone jack. All i can ever find is schematics for the circuitry and nothing on how to turn that into what i want. The "Little Gem" appears to have only a guitar jack input, and a headphone jack output. The "Little Gem MKII" appears to have a speaker but not a headphone jack output. And The "Ruby" appears only to have guitar jacks In & Out, and nothing else. Near as i can tell, what I'm looking for is a mixture of these three amps. Is there something I'm not getting here. I'm really confused. For eg, I look at this pic below of the ruby and all i see is circuitry (Which i understand) but nothing about where all those fkn wires are going to. I found all these designs at http://runoffgroove.com/littlegem.html & http://runoffgroove.com/ruby.html I didnt wanna bother anyone here with this as i wanted to figure it all out myself, but i'm totally lost. Any help woudl be greatly appreciated......Ansil, lovekraft? Edited October 6, 2004 by Boba_Fret Quote Link to comment Share on other sites More sharing options...
Boba_Fret Posted October 6, 2004 Author Report Share Posted October 6, 2004 With reguards to the guitar jack In & Out, would the out work as a headphone jack? Quote Link to comment Share on other sites More sharing options...
lovekraft Posted October 6, 2004 Report Share Posted October 6, 2004 ...I look at this pic below of the ruby and all i see is circuitry (Which i understand) but nothing about where all those fkn wires are going to... Take a look at the perfboard layout - it's easier to read. I haven't built this one, but I'll try to walk you through the photo from the layout. Clockwise from the upper left corner, the green lead is the input, the orange lead connects to lugs 1 and 2 on the gain pot, the next green lead connects to lug 2 of the volume pot, red connects to the + side of the 9 volt battery, blue connects to lug 3 of the volume pot, yellow connects to lug 3 of the gain pot, and the second orange wire is the output. The three grey wires appear to be ground leads (not necessarily the way I would have done it, but since I don't have any idea about the case or power supply setup, it might be ideal for the builder's application). Does that make it easier to follow? Quote Link to comment Share on other sites More sharing options...
Slabbefusk Posted October 6, 2004 Report Share Posted October 6, 2004 Yeah that looks like something i could finish! Cool, thx Boba_Fret. And BTW what does the ground do and where should i connect ground cables? Quote Link to comment Share on other sites More sharing options...
ansil Posted October 6, 2004 Report Share Posted October 6, 2004 the ground is the negative side of the battery and the other side of the input and output jack. Quote Link to comment Share on other sites More sharing options...
Slabbefusk Posted October 6, 2004 Report Share Posted October 6, 2004 so i should connect all ground wires to - ? Quote Link to comment Share on other sites More sharing options...
lovekraft Posted October 6, 2004 Report Share Posted October 6, 2004 (edited) No, connect them just like Ansil said - one to the input jack ground, one to the output jack ground, and one to the battery grouind. <edit> Sorry , I missed your second question back there at the beginning - yes, you could wire the output jack to drive a set of headphones, but the circuit is designed to drive an 8 ohm load, so higher impedance headphones won't work as well. Edited October 6, 2004 by lovekraft Quote Link to comment Share on other sites More sharing options...
javacody Posted October 7, 2004 Report Share Posted October 7, 2004 I've got a Ruby with the Bassman mods running through a Jensen 8" Vintage Reissue speaker in a Walmart speaker cab. This is a great sounding, 1/2 watt amp. A couple of warnings/suggestions: Keep your input and output wires as far away as physically possible from the power wires. If they are too close, or wrapped around each other, you will get extra noise from the power and it may cause oscillation. Buy a couple of JRC 386's (the chip used in the Smoky) and a couple of LM386's (there are 4 different versions of these, seen as LM386n where n = 1 through 4, you want probably 3 or 4, they handle more voltage) and use an 8 pin socket. This way you can mix and match and see if one of the chips sounds better to your ears. Your amp will run cleaner with higher voltage. Use 12 volts if you can. For a cigarette box amp, I honestly prefer the Smoky. Tiny components count and sounds excellent. My next project related to this is to take the buffer from the Little Gem and use a higher wattage 12 volt chip (7 watts). Quote Link to comment Share on other sites More sharing options...
Slabbefusk Posted October 7, 2004 Report Share Posted October 7, 2004 Okay i think i know how to ground it now, thx. Quote Link to comment Share on other sites More sharing options...
Boba_Fret Posted October 7, 2004 Author Report Share Posted October 7, 2004 Ah Cheers all. I'm starting to wrap my head around it now. The grounding info was most useful as well. Now I have to worry about finding parts for the "Ruby". I remember a while ago when "Benno" was asking about the same thing, someone gave him a Bill Of Materials with Dick Smith part numbers etc, for the "Little Gem" (when he was planning to build it into a guitar). If someone could whip that up for me for the "Ruby" that would be really helpful! Would save me a few hours in DS trying to figure out what i need. If not, no worries. Thanks, I'll be sure to ask if i have a problem. Quote Link to comment Share on other sites More sharing options...
kenneth_b Posted October 7, 2004 Report Share Posted October 7, 2004 (edited) Javacody: I'd be really interested in your design for a little gem like amp with 7 watts out. Could you let me know what chip you're going to use and what other mods need to be made? What I'd really like to learn how to make is a 10-12 watt output clean amp, with reverb. Edited October 7, 2004 by kenneth_b Quote Link to comment Share on other sites More sharing options...
lovekraft Posted October 7, 2004 Report Share Posted October 7, 2004 (edited) If someone could whip that up for me for the "Ruby" that would be really helpful! Would save me a few hours in DS trying to figure out what i need. Just take Benno's BOM, eliminate the two pots listed, add a 10K pot (R7506), a 1K pot (R7502), an MPF102 (Z1832), the 10 ohm resistor Ansil and I left out of the original list (R1626), replace the .01uF cap (R3012) with a .1uF (R3025), add a second .047uF (R3021) and find the other resistors associated with the input - they're 1/8 watt or 1/4 watt (your choice), and I'm assuming that you can find the values. Somebody want to check me on this, I might have missed something - the Ruby BOM I wrote out for somebody is here, and benno's Little Gem parts list w/ DSE part #s is here. HTH <EDIT> Now here's a guy who went way overboard on his Ruby build He's running a 12 volt wallwart for power ( as suggested earlier by javacody). Building a Ruby Edited October 7, 2004 by lovekraft Quote Link to comment Share on other sites More sharing options...
Hotrock Posted October 8, 2004 Report Share Posted October 8, 2004 .... for the "Little Gem" (when he was planning to build it into a guitar). I was looking at the polished-turd-ocaster last night wondering what I was going to do with it. The finish has got to come off as it's just not funky enough. This sounds like a wicked idea. Could I mount two little speakers in the guitar top and drive them using this amp? Any suggestions on type of speakers? Nice one dudes Quote Link to comment Share on other sites More sharing options...
Slabbefusk Posted October 9, 2004 Report Share Posted October 9, 2004 (edited) Okay i'm thinking off building this little amp too, but what i wonder about is where do i connect speaker + and - ? Could you please mark it out for me on this picture? PS: I think i have an idea of where to connect it but i'm not really sure. Edited October 9, 2004 by Slabbefusk Quote Link to comment Share on other sites More sharing options...
lovekraft Posted October 9, 2004 Report Share Posted October 9, 2004 The speaker hooks between the center lug of the 25 ohm pot (not shown here) and ground (GND). Quote Link to comment Share on other sites More sharing options...
Slabbefusk Posted October 9, 2004 Report Share Posted October 9, 2004 Cool, thx man. Quote Link to comment Share on other sites More sharing options...
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